The objectives of this project are two-fold: 1) define factors which selectively induce or depress antibody production in a given Ig class, 2) determine the role of selective antibody induction in resistance or susceptibility to neoplastic or infectious diseases. Syrian hamster has been the most useful animal model although other rodents and even lower vertebrates are used. Antibody production to purified protein antigens in a particular Ig class is detected by a variety of techniques such as radio-immunoassay, gel diffusion, immunoelectrophoresis and Jerne plaque assay. Immunoglobulins are isolated for study and characterization by ion exchange (DEAE), gel filtration (Sephadex), electrophoresis (Pevikon) and affinity chromatography techniques. Tissue culture synthesis with 14C-amino acids and microscopy with fluorescein-tagged antibodies are also used. Tumor models include neoplasma induced by polyoma and SV-40 viruses and the carcinogen DMBA.